Nowadays it is known to provide tanks for motor vehicles which are substantially constituted by very capacious containers into which the insertion of the fuel is done by way of an adapted inlet.
Such tanks are usually arranged below the loading surface of the vehicle, at preset heights both from the ground and from the chassis, in a sheltered area, usually in the space between the axles of two wheels.
Conventional tanks suffer a number of problems. First of all their great capacity has entailed the provision of nozzles for pumps for dispensing fuel which have a high flow-rate, since they necessarily have to dispense as much as hundreds of liters per minute in order to fill such tanks.
Such nozzles have standardized dimensions for the dispensing duct, which must be placed with the end tip in abutment in the inlet, and must then dispense the fuel at high speed. This entails the necessity that the dispensing duct must be positioned correctly in the inlet, usually at right angles to it in order to prevent one or more drawbacks from occurring, which include: splashing and backing-up owing to cross-sections which are of insufficient capacity for the flow-rate of the dispensing nozzle, or arrest of the flow of fuel from the nozzle owing to the automatic shut-off thereof.
Such method of positioning creates problems when the distance between the loading surface of the vehicle/trailer and the inlet is lower than the overall height that the nozzle has to assume in the condition in which the dispensing duct is correctly positioned in the inlet.
This entails the necessity to position the nozzle incorrectly, with consequent non-optimal positioning in axial alignment of the dispensing duct in the inlet and consequent non-optimal dispensing of the fuel, given that it does not flow axially to the inlet, and with an increase in the total time required to carry out the complete delivery.
Furthermore, in conventional tanks there is the problem of preventing the drawing-off for example of Diesel fuel; thus solutions of the mechanical type are known, in which it is sought substantially to reduce to the minimum the cross-section of entry to the tank in order to obstruct the introduction into it of flexible tubes for extracting the fuel.
In such conventional solutions, it is sought to prevent access to the tank using a tube, which is arranged between the entry point of the refueling inlet and the inside of the tank proper, and which contains a perforated metallic net or a “cobweb” of baffles, which are arranged on multiple levels and mutually offset.
These solutions, which therefore consist substantially of using a mechanical obstruction, although they provide a sufficient level of barring, also make it difficult to get liquid into the tank, for example Diesel fuel, when refueling, given that the Diesel fuel is forced to be deviated and turned back in several directions, in a chaotic manner and not in the direction of flow, thus forcing the person carrying out the refueling to choke the flow of fuel, increasing the time necessary to conclude the filling of the tank, so as to avert the sudden release of the nozzle by the intervention of the safety valve of the nozzle, and the interruption of the flow.
Furthermore if the barrier system against extracting Diesel fuel is arranged on the bottom of the tube of the anti-siphoning device fitted on the tank, such tube will be submerged completely once the tank has been filled with fuel.
In this case, once the cap of the tank is unscrewed, it is possible to easily extract the Diesel fuel comprised between the surface of the liquid and the bottom of the tube.
Considering that some tanks have a very large footprint in plan view, which generates capacities of as much as 1000 liters, it is easy to see that a few centimeters of Diesel fuel multiplied by the horizontal surface of the fuel contained in the tank translates to many dozens of liters of fuel that can be easily removed.
A further problem is constituted by the necessity to connect the anti-siphoning device fitted with the obstruction to the mouth of the tank; the conventional coupling systems involve either the use of metallic elements to be deformed, such as, for example, metallic tongues, or perforation and riveting of an anti-theft ring onto the tank body.
All such conventional systems require operations of greater or lesser length and special equipment, and they still allow ill-intended individuals, properly equipped, to remove the device.